Acoustic-cinematographic apparatus



Oct. 20, 1925. 1,557,678

J. ENGL ET AL ACOUSTIC CINEMATOGRAPHIC APPARATUS Original Filed April 4, 1921 MICROPHONE FILM STAGE All VIII

llllllll SCREEN Patented Oct. 20, 1925.

UNITED STATES PATENT OFFICE.

JOSE! ENGL AND JOSEPH KASSOLLE, F BERLIN-GRUNEWALD, AND HANS VOGI, 0F BERLIN-WILHEBSDORI, GERMANY, ASSIGNORS T0 TRI-ERGON, LIMITED, OF ZURICH, SWITZERLAND, A CORPORATION OF SWITZERLAND.

ACOUSTIC-CINEMATOGRAPHIC APPARATUS.

Original application filed April 4, 1921, Serial No. 458,629. Divided and this application filed October 29, 1924. Serial No. 748,741.

To all whom it may concern:

Be it known that we, J osnr ENGL, J osErH MAssoLLE, and HANS Vocr, citizens of the German Republic, residing, respectively, at Berlin-(irrunewald, 'Berlin-Grunewald, and Berlin-\Vilmersdorf, Germany, have invented certain new and useful Improvements in Acoustic Oinematographic Apparatus, of which the following is a specification.

The invention relates to improvements in acoustic-cinematographic apparatus, that is to say apparatus in which moving pictures are made and sounds accompanying the pictures are simultaneously recorded, the picture and sound records being, for example, recorded upon the same film; the pictures and sounds subsequently being synchronously reproduced by means involving the passage'of light thru the positive film made from the negative thus produced.

An object of the present invention is the improvement of the quality and volume of the sound recorded and subsequently reproduced by means involving the use of amplifiers in such a way as to prevent certain electrical disturbances and consequent distortion of the sound-modulated current and the sound itself as finally reproduced. The present aplication is a division of our application,

gerial No. 458,629, filed April 4, 1921 and entitled improvements in arrangement for acoustic-cinematography.

In making the sound record on the negative film, the sound affects a microphone whereby a corresponding sound-modulated current is set up which current affects a re cording light, the variation of which makes a photographic record upon the negative film, the variations of which should correspond to the sound which is to be recorded. In reproducing, light from a suitable source is caused to pass thru the moving positive film, which has been made from the negative film, thus produced, and this light falls upon a suitable light-sensitive device, such as a photo-electric cell.

The variations in the photo-electric cell caused by the action of the ligth thereupon,

set up acoustically-modulated currents, that is current varying in correspondence with the soundto be reproduced, and these currents actuate a form oftelephone or loud speaker whereby the sound is reproduced. The above generally described form of apparatus is, of course, well known.

These known arrangements have, however, important disadvantages. The acousticallymodulated currents in both receiving and reproducing are very small being, for example, of the order of magnitude 10' to 10 amperes, the result of which is that the sound produced, Without amplification, will be too weak for suitable reproduction in a large hall or the like. Furthermore, the use of amplifiers in such systems present various difficulties. The employment of low-frequency amplifiers has the disadvantage that, in accordance with prior practice, low frequency transformers have to be used as coupling means. Such use causes a falsification of the sound reproduced and of the tone color of the same and also amplifies all disturbing noises. This is for the reason that strong electromagnetic disturbances are caused in moving picture work by various factors, the efiect of which is especially marked on the amplifier circuit of the acoustic system if the use of amplifiers in the latter is attempted. These effects are produced for example, by the projection arc lamp used for making pict res and the projection machine motor in the reproducing system, (both closely adjacent to the acoustic operations), the lamp by which the stage is lighted for the recording system, etc. If low-frequency transformers are used in the connections in the acoustic system, distortion of the acoustically-modulated currents is produced, because of magnetic hysteresis effects, undesired resonance and disturbing low-frequency alternating fields, afiecting the transformers, as the result of causes, such as those mentioned.

In consequence of the above, such methods of amplification have hitherto not obtained importance in practice in acoustic-cinematography. The impression received by the audience, which should be one of synchronism between the optical and the accompanying acoustic operation, may be annulled by distorted reproduction of the speech or other sounds, especially if ampli- Y which they may be influenced.

The arrangement consists in the combination of the recording and reproducing means, (microphone, photocells, etc.) with amplifiers (vacuum tubes) -which possess no inertia, and whose elements are galvanically,

i. e., resistance-coupled without the-use of low frequency transformers. The recording and re roducing means referred to, comprising, wlth the amplifiers, the elements of the system, include the microphone in the recording system and the photo cell in the reproducin system and'also the telephone or loud spea er b which the sound is eventually reproduct in the reproducing system. The invention further consists in the combination and arrangement of parts all as will be more fully stated in the following specification, and particularly pointed out in the appended claims.

The invention may also be carried out by the provision of inertia-free high frequency amp ifiers coupled together by high frequency transformers having air cores and conse uently free from iron, this arrange ment eing for use in a system in which high frequency alternatin current from a suitable source is employe Such high frequency transformers are relatively insensitive to disturbances by low frequency fields.

In our said application, Serial No.458,629, the species of invention involvin the use of high frequency transformers re erred to is included and in the present application the species of invention involving the use of resistance coupling will be claimed.

In order that the invention may be more clearl understood, attention is hereby directe to the accompan ing drawings illustrating diagrammatica ly by way of example, recording and reproducing systems, in which the invention may be used.

Referring to the drawings, Fig. 1 represents diagrammatically a system for simultaneously recording, on a moving film, pictures and the accompanying sounds; Fig. 2 represents diagrammatically a system for reproducing, from a moving film, pictures and the accompanying sounds.

In Fig. 1 a pair of thermionic amplifiers are indicated as resistance-coupled in a system for recording sound on a moving film.

The film is indicated diagrammatically at 1,

being made for example of actors upon a stage 4 illuminated in the usual way by electric lam s, which are indicated at 55.

The speec or other sounds produced b the actors or accompan ing their action fa 1 upon a micro hone in icated diagrammatically at 6. current is accordmgl produced in the circuit 7, leading from t e microphone, which current is sound-modulated, that is it fluctuates in correspondence with the sound roducing the same. This circuit leads to a t ermionic amplifier 8, one side of the circuit being connected to the usual filament 9 of the am lifier and the other side to the grid 10, in tie usual manner.

Amplified current flows from the plate 11 of amplifier 8 to the grid 10 of a second amplifier 8, it being understood that as many am lifiers are used in this system as is found desirable. From the last am lifier of the series, illustrated as the ampli er 8", an output circuit 12 is indicated as leading to a recordin lamp indicated diagrammatically at 13. e illumination of thislamp is varied in accordance with the sound modulated current received thereb and the light thus varied falls upon the fi m 1 to make a negative record corres onding to the sound as is well known. e amplifiers of the system are coupled'together by resistances resistance 15 being indicated as connected across the output circuit of amplifier 8 in the well known manner. Similarly the microphone 6 is illustrated as resistance coupled to the first amplifier 8, resistance 15 bein shown as connected across the circuit leading from the microphone to the filament and grid of the tube 8. Batteries, 16, 16" and 16 are conventionall indicated as included in the circuits 7, 1 between the amplifiers, and 12 extending between am liticr 8 and the recording lamp 13, this lieing, of course, common practice. A resistance 15 is also indicated as included in the circuit 12 leading from the last amplifier. Condensers 18 and 18" are indicated in the grid leads of amplifiers 8 and 8 merely by way of example. It may be noted that coupling resistance 15 for the microphone corresponds to the resistance described in our copendingI application Serial No. 458,632, entitled et 0d for the control of electric currents by power of sounds, filed April 4, 1921, and there stated to be the couplin' resistance of the microphone for ampli ying or intensifying tubes.

Fig. 2 represents by way of exam le, the manner in which the invention may e used in the reproducing system. As there shown, the positive film 1 bears the positive sound and pictme reco; is The pictures are prothe telephone.

jected by a suitable light source, such as the arc lamp indicated diagrammatically at 19, the light from the same being indicated conventionally as passing thru a lens 20, thus thru the filament and then by lens 21 upon the screen 22. In the accompanying acoustical system, light from a suitable source 23 is projected through the sound record on film 1 and falls upon photo-electric cell 24. The cell 24 is connected by a circuit 25 with a suitable amplifying tube 26. The two sides of the circuit are indicated conventionally as extending to the grid and filament of tube 26, a resistance coupling 27 being indicated as connected across the grid and filament leads of tube 26. The output circuit of tube 26 is connected to the next amplifier 28 of the series, aresistance coupling 29 being indicated as connected across the grid and filament leads of the second amplifier. The plate and filament of the last tube are indicated as connected by circuit 32 to the telephone indicated diagrammatically at 30 by which the sound is reproduced, and resistance 31 being indicated as connected around Sound modulated current' is produced by the photo electric cell 24 and this is amplified by the amplifiers without distortion and eventually causes reproduction of sound by the telephone or loud speaker 30.

We claim:

1. In acoustic-cinematographic apparatus, including an electric device,'adapted to cause electro-magnetic disturbances in adjacent electrical apparatus, the combination of means for producing an acoustically modulated electric current, a plurality of thermionic amplifiers, and connections between all of said elements including resistance couplings between adjacent amplifiers, adapted to avoid the disturbing effect of said electric device on the circuits of said amplifiers.

2. In acoustic-cinematographic apparatus, including an electric device adapted to cause electro-magnetic disturbances in adjacent electrical apparatus, the combination of ele- 'ments of an acoustic systeni, comprising means for producing an acoustically-modulated electric current and a plurality of thermionic amplifiers, and connections comprising resistance couplings between all of said elements, adapted to avoid the disturbing effect of said electrical device on the circuits of said amplifiers.

3. In acoustic-cinematographic apparatus, including a light source of a moving picture apparatus, adapted to cause electro-magnetic disturbances in adjacent electrical apparatus,

the combination of elements of an acoustic system, comprising means for producing an acoustic ally-modulated electric current and a plurality of thermionic amplifiers and connections comprising resistance couplings between various of said elements, adapted to avoid the disturbing effect of said light source on the circuits of said amplifiers.

4. In acoustic-cinematographic apparatus, including an electric device adapted to cause electro-magnetic disturbances in adjacent electrical apparatus, the combination of means for producing an acoustically-modulated electric current, a thermionic amplifier, and a resistance coupling for connecting said first named means to said amplifier, to avoid the disturbing efi'ect of said electrical device on the circuits of said amplifier.

5. In acoustic-cinematographic apparatus including an electric device adapted to cause electro-magnetic disturbances in adjacent electrical apparatus, the combination of a microphone, a thermionic amplifier, and a resistance coupling for connecting said microphone to said amplifier, to avoid the disturbing efi'ect of said electrical device on the circuit of said amplifier.

6. In acoustic-cinematographic apparatus, the combination of a moving picture machine having an electric light source, capable of causing electro-magnetic disturbances in adjacent apparatus, acoustic apparatus comprising means for producing an acousticallymodulated electric current, thermionic ainplifying means and connections between various of said means comprising resistance couplings, said acoustic apparatus operating simultaneously with said moving picture machine and being close enough thereto to be affected by disturbances produced by said light source.

JOSEF ENGL. JOSEPH MASSOLLE. HANS VOGT. 

